1. Field of the Invention
The present invention relates to a liquid crystal dispensing apparatus that dispenses a controlled amount of liquid crystal, with the dispensed amount depending on the tension of a spring.
2. Description of the Related Art
Portable electric devices, such as mobile phones, personal digital assistants (PDA), and notebook computers, often require thin, lightweight, and efficient flat panel displays. There are various types of flat panel displays, including liquid crystal displays (LCD), plasma display panels (PDP), field emission displays (FED), and vacuum fluorescent displays (VFD). Of these, LCDs have the advantages of being widely available, easy to use, and superior image quality.
The LCD displays information based on the refractive anisotropy of liquid crystal. As shown in FIG. 1, an LCD 1 comprises a lower substrate 5, an upper substrate 3, and a liquid crystal layer 7 that is disposed between the lower substrate 5 and the upper substrate 3. The lower substrate 5 includes an array of driving devices and a plurality of pixels (not shown). The individual driving devices are usually thin film transistors (TFT) located at each pixel. The upper substrate 3 includes color filters for producing color. Furthermore, a pixel electrode and a common electrode are respectively formed on the lower substrate 5 and on the upper substrate 3. Alignment layers are formed on the lower substrate 5 and on the upper substrate 3. The alignment layers are used to uniformly align the liquid crystal layer 7.
The lower substrate 5 and the upper substrate 3 are attached using a sealing material 9. In operation, the liquid crystal molecules are initially oriented by the alignment layers, and then reoriented by the driving device according to video information so as to control the light transmitted through the liquid crystal layer to produce an image.
The fabrication of an LCD device requires the forming of driving devices on the lower substrate 5, the forming of color filters on the upper substrate 3, and injecting liquid crystal in a cell process (described subsequently). Those processes will be described with reference to FIG. 2.
Initially, in step S101, a plurality of perpendicularly crossing gate lines and data lines are formed on the lower substrate 5, thereby defining pixel areas between the gate and data lines. A thin film transistor that is connected to a gate line and to a data line is formed in each pixel area. Also, a pixel electrode that is connected to the thin film transistor is formed in each pixel area. This enables driving the liquid crystal layer according to signals applied through the thin film transistor.
In step S104, R (Red), G (Green), and B (Blue) color filter layers (for reproducing color) and a common electrode are formed on the upper substrate 3. Then, in steps S102 and S105, alignment layers are formed on the lower substrate 5 and on the upper substrate 3. The alignment layers are rubbed to induce surface anchoring (establishing a pretilt angle and an alignment direction) for the liquid crystal molecules. Thereafter, in step S103, spacers for maintaining a constant, uniform cell gap is dispersed onto the lower substrate 5.
Then, in steps S106 and S107, a sealing material is applied onto outer portions such that the resulting seal has a liquid crystal injection opening. That opening is used to inject liquid crystal The upper substrate 3 and the lower substrate 5 are then attached together by compressing the sealing material.
While the foregoing has described forming a single panel area, in practice it is economically beneficial to form a plurality of unit panel areas. To this end, the lower substrate 5 and the upper substrate 3 large glass substrates that contain a plurality of unit panel areas, each having a driving device array or a color filter array surrounded by sealant having a liquid crystal injection opening. To isolate the individual unit panels, in step S108 the assembled glass substrates are cut into individual unit panels. Thereafter, in step S109 liquid crystal is injected into the individual unit panels by way of liquid crystal injection openings, which are then sealed. Finally, in step S110 the individual unit panels are tested.
As described above, liquid crystal is injected through a liquid crystal injection opening. Injection of the liquid crystal is usually pressure induced. FIG. 3 shows a device for injecting liquid crystal. As shown, a container 12 that contains liquid crystal, and a plurality of individual unit panels 1 are placed in a vacuum chamber 10 such that the individual unit panels 1 are located above the container 12. The vacuum chamber 10 is connected to a vacuum pump that produces a predetermined vacuum. A liquid crystal display panel moving device (not shown) moves the individual unit panels 1 into contact with the liquid crystal 14 such that each injection opening 16 is in the liquid crystal 14.
When the vacuum within the chamber 10 is increased by inflowing nitrogen gas (N2) the liquid crystal 14 is injected into the individual unit panels 1 through the liquid crystal injection openings 16. After the liquid crystal 14 entirely fills the individual unit panels 1, the liquid crystal injection opening 16 of each individual unit panel 1 is sealed by a sealing material.
While generally successful, there are problems with pressure injecting liquid crystal 14. First, the time required for the liquid crystal 14 to inject into the individual unit panels 1 is rather long. Generally, the gap between the driving device array substrate and the color filter substrate is very narrow, on the order of micrometers. Thus, only a very small amount of liquid crystal 14 is injected into per unit time. For example, it takes about 8 hours to inject liquid crystal 14 into an individual 15 inch unit panel 1. This decreases fabrication efficiency.
Second, liquid crystal 14 consumption is excessive. Only a small amount of liquid crystal 14 in the container 12 is actually injected into the individual unit panels 1. Since liquid crystal 14 exposed to air or to certain other gases can be contaminated by chemical reaction the remaining liquid crystal 14 should be discarded. This increases liquid crystal fabrication costs.
Therefore, an improved method and apparatus of disposing a liquid crystal between substrates would be beneficial.
Accordingly, the present invention is directed to provide a liquid crystal dispensing apparatus for directly dropping liquid crystal onto a glass substrate that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An advantage of the present invention is to provide a liquid crystal dispensing apparatus enables control of the amount of liquid crystal that is dropped onto the substrate using the tension of a spring.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a liquid crystal dispensing apparatus having a liquid crystal container for holding a liquid crystal. The liquid crystal container is inside a case. A needle sheet is disposed on a lower portion of the liquid crystal container. The needle sheet includes an opening through which liquid crystal in the liquid crystal container is discharged. A movable needle is inserted into the liquid crystal container. A spring in a receiving case biases the needle toward the opening such that the opening tends to close. A tension controller connected to the receiving case controls the tension of the spring by controlling the spring length. A solenoid, beneficially with the aid of a bar magnetic, selectively produces a magnetic force that moves the needle away from the opening. A nozzle disposed on a lower portion of the liquid crystal container emits liquid crystal when the opening is open.
The spring is beneficially located between a spring fixer on the needle and an end portion of the tension controller. As the length of the spring is adjusted, the tension applied to the needle is changed. Consequently, after the magnetic force is removed the spring returns the needle so as to close the opening. Beneficially, the time that the opening is opened depends on the spring tension. Furthermore, the amount of liquid crystal that passes through the nozzle depends on the spring tension.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.